Transfer copying material



Aug. 1, 1939. J GRQAK 2,168,098

TRANSFER COPYING MATERIAL Filed Feb. 16, 1938 Joiref ik-aaK Patented Aug. 1, 1939' UNITED STATES PATENT OFFICE Application February 16, 1938, Serial No. 190,881 In Great Britain February 3, 1938 12 Claims.

It is known to produce a copy of an impression made on an original sheet with a writing instrument, such as a pencil or a typewriter, by providing between the original and the copy sheets a layer coated either on a thin intermediate sheet or on the back of the original sheet and containing a colouring matter which is transferred to the copy sheet under the pressure of the writing instrument.

It has been proposed to dispense with the intermediate layer containing transferable colouring matter by applying to the rear surface of the original sheet a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance applied to the upper surface of the copy sheet when the treated surfaces of the sheets are pressed into contact during copying. The presence of moisture is necessary to bring about the reaction, and for this purpose it has been proposed to incorporate a hygroscopic substance with the reactive ingredients. The reactive coatings hitherto proposed have the drawback of not retaining their reactivity for sufficiently long periods or of being sticky and smearable, and in some cases the coloured marking will be formed on the rear surface of the original sheet as well as on the copy sheet.

It is an object of the present invention to provide a coating on the rear surface of the original sheet which will retainits moisture and therefore as reactivity, for long periods, and which at the same time remains dry and nonsticky to the touch and prevents or minimizes the formation of the colouring matter on the rear surface of the original sheet.

According to this invention, the rear surface of the original sheet is provided with a coating composed of at least one hard waxy substance as hereinafter defined containing dispersed there in an admixture of starch, a hydroscopic substance, such as glycerin, and the reaction substance.

By the expression hard waxy substance there is to be understood a wax or waxy substance which is hard and dry at normal temperature. Suitable substances of this kind are carnauba wax, montan wax, paraflln wax and white wax.

The coating according to the invention is hard and dry, and the dispersion of starch particles, which bind the hygroscopic and reactive substances, within the waxy substance ensures a stable composition which retains its reactivity for long periods. As a suitable starch there may be mentioned wheat starch.

The reactive substance may be applied to the copy sheet in any other suitable manner, for example by impregnating or coating it with a solution or suspension of the reactive substance. Alternatively, the latter may be incorporated with 5 the pulp during the manufacture of the paper. It is preferable to apply the reactive substance in conjunction with a fixative, such as gum tragacanth, and it has been found advantageous to use a coating composition made by incorporating the reactive substance with an alcoholic base of the kind used in making aniline printing inks. A layer prepared with such a coating composition gives copies which are highly resistant to smudging. Suitable reactive substances are ferrous sulphate and tannin, which on being admixed produce a dark coloured reaction product. One of these substances is applied to the original sheet and the other to the copy sheet.

Transfer copying materials made in accordance with the invention are shown in cross section on a greatly exaggerated scale in the accompanying drawing, in which Fig. 1 shows a pair of original and copy sheets,

Fig. 2 shows a modified form of original sheet,

Fig. 3 shows a modified form of copy sheet, and Fig. 4 shows an original sheet and a modified form of copy sheet.

Fig. 1 shows an original sheet i provided with a waxy coating 2 prepared in accordance with the invention, and a copy sheet 3 provided with a coating 4 prepared, for example, from a solution of a suitable reactive substance and gum tragacanth or other fixative in alcohol or other solvent.

In order to reduce the risk of the active substances reacting prematurely when the treated surfaces of the sheets are brought into contact, it is of advantage as shown in Fig. 2 to apply a. very thin protective film 5, for example of paraffin wax, over the coating 2 on the original sheet I. Under the pressure of the writing instrument this thin protective film is broken, so that reaction between the substances contained in the treated surfaces can occur.

When it is desired to make several copies, the copy sheets may be coated as shown in Fig. 3 on the underside with a waxy coating 2 similar to that applied to the original sheet. The copy sheets 3 will then contain one of the reactive substances in the coatings l on their upper surfaces and the other reactive substances in the coatings 2 on their lower surfaces, and if the sheet is thin there is a risk that the reactive substances may intermix within the sheet to produce a coloured reaction product. To avoid this draw- -ferrous sulphate back the uppei coatings 4 and the lower waxy coatings 2 of the copy sheets may contain the same reactive substance, some of the sheets containing one of the reactive substances, for example tannin, and other sheets containing the other reactive substance, for example ferrous sulphate. During copying the two different kinds of sheets will'then be arranged in alternation with the waxy coatings 2 downwards. It may be necessary by suitable marking or colouration to distinguish the sides of the copy sheets and also to distinguish the different sheets according to the reactive substances which they contain.

By suitable choice of reactive substances it is possible to obtain reaction products of various colours, and for certain purposes, for example in bookkeeping, it may be of advantage to arrange that different colours are produced in different areas of the copy sheet as shown in Fig. 4. For example, when using an original sheet containing a waxy coating 2 of ferrous sulphate, the copy sheet 3 may be treated or coated'in a part of its area 4' with tannin to produce a dark co1ouration, and in another part of its area 4" with potassium thiocyanate to produce a red colouration.

The following example illustrates the invention, the parts being by weight:

The coating composition for the original sheet is prepared as follows: 41 parts of wheat starch, 50 parts of glycerin and 1-2 parts of gum tragacanth are mixed together, and there is then added thereto a mixture of 48 parts of powdered (FeSOdHzO), 25 parts of glycerin and 2 parts of phenol. The whole is thoroughly mixed and allowed to stand for 24 hours to give a stiff pasty mass. 158 parts of carnauba wax, parts of paraflin wax and 50 parts of white wax are heated to melting and allowed to stand for a short time at 50-60 C. This mixture is then thoroughly admixed with the aforesaid pasty mass at a temperature of about 50 C. The rsulting'composition is applied to a paper sheet in any suitable manner, for example by spraying or by means of a coating roller.

The copy sheet is coated with a solution made by dissolving 30 parts of tannin, 50 parts of gallic acid, 20 parts of oak tannin and 10-20 parts of gum tragacanth or other fixative in alcohol.

I claim:

1. In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried on a copy sheet when transferred thereto from the original sheet during copying, an original sheet which is provided with a coating composed of at least one hard waxy substance containing dispersed therein an admixture of starch, a hygroscopic substance and a reactive substance as aforesaid.

2. In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried on a copy sheet when transfered thereto from the original sheet during copyin an original sheet which is provided with a coating composed of at least one hard waxy substance containing dispersed therein an admixture of starch, glycerin and a reactive substance as aforesaid.

3. In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with orginal sheet during copying, an original sheet which is provided with a coating of at least one substance selected. from the group camauba wax, montan wax, paraffin wax and white wax and containing dispersed therein an admixture of starch, a hygroscopic substance and a reactive substance as aforesaid.

5. In a transfer copying system in'which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried on a copy sheet'when transferred thereto from the original sheet during copying, an original sheet which is provided with a coating composed of a mixture of carnauba wax, paraffin wax and white wax within which is dispersed an admixture of starch, a hygroscopic substance and a reactive substance as aforesaid.

6. In a transfer copying system in which an original sheet carries'a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried .on a copy sheet when transferred thereto from the original sheet during copying, an original sheet which is provided with a coating composed of at least one hard waxy substance containing dispersed therein an admixture of wheat starch, glycerin and one of the compounds, ferrous sulphate and tannin;

7. In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried on a copy sheet when transferred thereto from the original sheet during copying, an original sheet which is provided with a coating composed of at least one hard waxysubstance containing dispersed therein an admixture of starch, a hygroscopic substance and a reactive substance as aforesaid, the said coating having thereon a very thin protective film which can be broken through during copying to permit the transfer of the reactive substance onto the copy sheet.

8. In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried on a copy sheet when transferred thereto from the original sheet during copying, an original sheet which is provided with a coating composed of at least one hard waxy substance containing dispersed therein an admixture of starch, a hyroscopic substance and a reactive substance as aforesaid, the said coating having thereon a very thin protective film of paraffin wax which can be broken through during copying to permit the transfer of the reactive substance onto the copy ferred thereto from the original sheet during copying,.a copy sheet which, in addition to the reactive substance carried on its upper surface,

is provided on its under surface with a coating composed of at least one hard waxy substance containing dispersed therein an admixture of starch, a hygroscopic substance and a reactive substance of the kind carried by the original sheet.

10. In a transfer copying system in which an.

original sheet carries a reactive substance capable of producing acolouring matter by reaction with another appropriate reactive substance carried on the upper surface of a copy sheet when transferred thereto from the original sheet during copying, a copy sheet which, in addition to the reactive substance carried on its upper surface, is provided on its under surface with a coating composed of at least one hard waxy substance,

containing dispersed therein an admixture of starch, a hygroscopic substance and a reactive substance which is the same as that carried on the upper surface of the copy sheet.

11. In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance caaried on the upper surface of a copy sheet when transferred thereto from the original sheet during copying, a copy sheet which, in addition to the reactive substance carried on its upper surface, is provided on its under surface'with a. coating composed of at least one hard waxy substance containing dispersed therein an admixture of wheat starch, glycerin and a reactive substance of the kind carried by the original sheet.

12; In a transfer copying system in which an original sheet carries a reactive substance capable of producing a colouring matter by reaction with another appropriate reactive substance carried on the upper surface of a copy sheet when transferred thereto from the original sheet during copying, a copy sheet which, in addition to the reactive substance carried on its upper surface, is provided on its under surface with a coating composed of at least one hard waxy substance containing dispersed therein an admixture of wheat starch, glycerin and a reactive substance which is the copy sheet.

JOSEF. GROAK; as 

